1. Field of the Invention
The present invention concerns a laying-down system for building together with plant for the primal cutting-up of meat items, namely half carcasses of pigs. The invention also concerns a fully-automatic system for the primal cutting-up of meat items, namely half carcasses of pigs, and comprising a laying-down module, a vision-based detection system for the determination of relevant fix points on meat items, a calculation unit with interface for the controlling of a positioning module and a sawing module. Moreover, the invention concerns a method based on a vision system for primal cutting-up of meat items.
The dividing-up of half pig carcasses is traditionally carried out by an operator placed at a conveyor belt on which the carcasses pass, in that he manually corrects (pulls/pushes) the half carcass in position for a saw (circular knife) which is disposed above the conveyor belt. With this method, use is made of an operator and a saw for each cut which is made in the half carcasses.
The way in which the correction of the half carcasses is typically carried out is that a line laser marker mounted on the individual saws irradiates the conveyor band immediately in front of the saw in an imaginary line through the blade of the saw, and the operator uses this laser beam in moving the half carcass manually so that this is sawn through in the desired place.
The above-mentioned method has several disadvantages. In the first place, the operator's work is monotonous and physically demanding, and operators who carry out this work are worn-out by the work after a relatively short period. Secondly, the positioning of the cut is based on the subjective judgment of the individual operator, so that the accuracy can fall with changing operators, inattention on the part of the operator, or if he has difficulty in maintaining the necessary concentration over longer periods of time. Thirdly, the definition of the correct knife positioning can change during the course of the production, which necessiates verbal communication of the changed requirements out to a number of operators, which involves possibilities of error.
2. Description of Related Art
Efforts have been made to automate the above-mentioned method, for example in DK B 161 656 there is disclosed a semi-automatic plant of the kind whereby an operator moves a position-provider coupled to a laser beam to the positions on the half carcass where he judges that the cuts shall be placed. When the laser beam irradiates the place of the cut, the operator activates an operating element, whereby the position of the position-provider is read into a control system. The positions of the cutting places are used to position the half carcasses and the subsequent saws, so that the different cuts are effected in accordance with the judgment of the operator. The publication also discloses a method for arranging the individual half carcasses so that their lengthways axes are positioned at right-angles to the feeding direction. With the said system, it is thus possible for human errors of judgment to be made in connection with the positioning which determines the cuts which are to be carried out in the half carcasses.
In DK T3 0 594 528, a system is disclosed by which, with the help of mechanical measuring of the half carcasses, it can carry out a tri-partition of these (ham and fore-end cuts). The arranging of the half carcasses to the correct angle takes place in connection with the measuring of fix points in the pig carcass, in that this is drawn over the surface of the conveyor by means of the mechanical measuring means.
The above-mentioned methods are based either on manual or mechanical localization of the fix points which form the starting point for the cutting-up positions.
DK B1 167 462 discloses a vision system for the determination of said fix points on the half of an animal carcass, said vision system being coupled to a computer for the implementation of picture analysis which, after the determination of the position of fix points in a manner which is not specified, is said to send control signals to mechanisms which are not further described, and which on the basis of the positioning of the fix points carry out the arranging of the carcass and of the system's tools for the cutting-up of said carcass.
However, several different patents and patent applications are to be found which deal with actual vision analyses of meat products, partly with the view of classifying meat products, e.g. for determining the market value, and partly to be able to determine the position of certain structures. Among these there are two German publications, DE C2 41 31 556 and DE A1 41 09 345, to which reference is made when, in connection with the present invention application, vision analysis/determination of fix points on half carcasses is discussed. The precondition for the present invention is thus that the position of the fix points on half carcasses, which are used as starting point for the determination of the individual cuts, takes place by means of said vision system. The vision system comprises a video camera which takes a picture of the half carcass while this passes under the camera on a conveyor. The camera is coupled to a computer, which with specially-developed software recognizes the contours and inner structure of the half carcass, such as e.g. vertebrae in the spine and the pubis. Hereafter, with great accuracy the computer calculates the positions of the individual fix points in relation to a given zero line. By means of the computer together with suitable interface and actuators, the positioning of the fix points in relation to the zero line can subsequently be used for effecting mutual positioning of the half carcasses/saws with starting point in a beforehand desired positioning of the cuts in relation to said positioning of said fix points. The positioning can take place either by effecting a displacement of the saws (saw blades) in the lateral direction, still with the blades arranged parallel with the transport direction, and/or by using conveyor plant which can be displaced in the transverse direction by means of actuators.
The above-mentioned method and system is particularly suitable for use when an ordinary “industrial cut” is to be made (double cut where the fore-end and hams are separated from the central piece) at right-angles to the lengthways direction of the carcass, where the half carcasses are transported with the lengthways direction arranged at right-angles to the direction of transport, and where the parting cuts are placed in relation to the positions of the fix points by positioning of the half carcasses on sideways-displaceable conveyors, and positioning of the saws in the sideways direction.
If only a ham cut is to be carried out, which is sometimes known as a “Belgian cut”, also in the following, it will not be possible to use the above-mentioned method for automatic parting of the carcass, in that a Belgian cut is effected as an inclined cut in relation to the lengthways direction of the carcass, though still in relation to the positioning of the relevant fix point on the half carcass. When carrying out the parting with this type of cut, it has thus hitherto been necessary to effect the cutting manually with manually-operated saws with laser marking of the positioning of the cut, in that the cut which is carried out here shall extend at an angle in relation to the direction of transport. Neither is the above-mentioned method particularly suitable when it is preferred to carry out an optimized industrial cut, which often involves the placing of the cuts at an angle which deviates from right-angles to the lengthways direction of the carcass.
These problems are further aggravated when the production rate has to be increased. Typically, a slaughter line as described above will be able to handle 3-500 carcasses an hour, but it is desirable to be able to have an automatic cutting system which can handle 1000-1200 carcasses or more per hours. One of the key problems in increasing the production rate is that the compromise between cutting quality and speed appears to be somewhere in the vicinity of about 0,4 meters per second for cutting speed. At higher cutting speeds a number of undesirable effects appear, such as crushing of bones whereby bone splinters can contaminate the finished meat items, the cut surfaces can be covered by fat which has been pulled out from the meat item to be cut, which is undesirable in the quality of the finished meat products. Furthermore, the carcasses can be forced into a undesirable position in relation to the rest of the cutting proceedings when the saws engage larger bones and the like. Furthermore, in order to be able to adjust the saws in relation to fixed points on the meat in order to carry out the desired cuts, it is advantageous that the saws come to a stand-still such that the gyroscopic effect of the saws will not have any influence on the positioning. By increasing the production speed it can be difficult to provide the necessary period of rest time for the saws in order to adjust them precisely.